Sedimentology, Resource Conservation Methods and Environmental Policy of Irrigated Row Crop Agriculture in the Salinas Valley, CA

1
Sedimentology, Resource Conservation Methods and
Environmental Policy of Irrigated Row Crop
Agriculture in the Salinas Valley, CA

• Don Kozlowski
• May 2001

2
Background

• 1972, Clean Water Act, Sect. 303(d)
• list fix pollution via TMDL
• Salinas River listed as impacted by
• sediment
• Beneficial uses the Endangered
• Species Act

• 2001, still no TMDL for the Salinas
• Salinas Sediment Study hired by
• state for technical assistance

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Possible Sources

• Natural processes
• Recreational use
• Mining

• Urban/suburban
• Grazing
• Viticulture

• Agriculture
• 15 of area is row crop agriculture (165,000 ha)
• 40 sediment of U.S. rivers from cultivated land
• ags contribution to the Salinas River?

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Objectives

• Determine
• Typical sediment yields from row crop ag fields
  due to irrigation and storm events during a
  season
• Efficiency of a particular best management
  practice, the water/sediment detention basin

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Methods
Site selection
Catchment construction
Filtration
Recording and analysis
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Methods (cont)

• Create model that predicts field erosion
• Determined from various event parameters
• Upscale the field data to watershed scale
• GIS model to get area slope
• Rainfall model
• For detention basins
• Compare sediment into basin to sediment out

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Results (15 events monitored 9 irrigation, 6
rainfall)
Erosion Analysis (example)
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Results (cont)
Erosion Model
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Still More Results

• Watershed Scale Erosion Estimates
• Rainfall 93 kilo-tonnes, 1.2 tonnes/ha
• Irrigation 141 kilo-tonnes, 1.7 tonnes/ha
• Total 234 kilo-tonnes, 2.9 tonnes/ha

CAUTION!!

• 60 of agricultural row cropland, slopes lt2.3
• Only a fraction of this made it to the Salinas
  River

• Efficiency of Detention Basin
• 100 for sand, at least 99 for silt/clay
• 211mg/L max outgoing 46,400 mg/L max incoming

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Discussion/Wrap-up

• Agricultural land use produces a lot of erosion
• Many BMPs are in place
• Detention basins appear to work well
• Improvements
• Storm erosion dynamics, need more data
• Slopes gt 2, need data
• Rain model

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Acknowledgements

• Farmers
• SSS team (Thor, Wendi, Adrian, Alana, Bronwyn,
  Joel, Julie)
• Mark Angelo, RWQCB
• Bryan Largay, Monterey Co. RCD
• NASA/EPA
• Dr. Sharon Anderson
• Dr. Lars Pierce
• Dr. Fred Watson